Lemma 6 (Weyl's inequality [1]})
For two matrices \(M \in \mathbb {C}^{m \times n}\) , \(N \in \mathbb {C}^{m \times n}\)  and any \(i\in [{\rm min}(m,n)]\) , \(|\sigma _{i}(M) - \sigma _{i}(N)| \le \Vert M - N\Vert \) .

